Patent application PCT/ES99/00413, from the same holder, which also refers a process for manufacturing printed circuit boards, discloses a process with several steps, which comprises carrying out a first selective engraving by machining or by etching on a first side of a plate of electro-conductive material and applying a dielectric material, by means of a jet molding operation, on said side of the plate of electro-conductive material. Prior to jet molding, the plate of electro-conductive material is subjected to a surface treatment for improving the junction capacitance, and a layer of an adhesive material is preferably applied onto said first engraved and superficially treated side.
A second selective engraving can also be carried out on a second side, opposite the first.
The process disclosed in said patent application ensures a strong junction between the conductive tracks and the dielectric substrate, but the jet molding implies an anisotropy in the jet molded dielectric (differentiated orientation of fibers in the zone next to the jet molding nozzles with regard to those farther away and which become stiff upon losing part of their fluidity) and properties that are sensitive to orientation, such as greater tensile strength in the sense of orientation lead to the boards having unwanted curving or bending in non-stable conditions (processing the plates and temperature variations), which can lead to endangering the integrity of the printed circuit (conductive layer to dielectric substrate junction).
U.S. Pat. No. 4,671,301 discloses the manufacture of a board carried out by continuously molding a mixture of resin and uniformly distributed filling materials.
The incorporation of filling materials in the resin is a well known technique for improving the physical and chemical properties thereof.